BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] The present invention is directed to sealing Organic Light Emitting Diodes (OLEDs)
and displays made of OLEDs.
Technical Background
[0002] As a result of the many potential applications for compact and efficient displays,
organic light-emitting diodes (OLEDs) are the focus of a tremendous amount of attention.
OLEDs include electrodes and organic layers. There are two types of electrodes an
anode and a cathode. There are also two types of organic layers a conducting layer
and an emissive layer. In conventional implementations, the OLED components are deployed
on a first substrate. The first substrate is typically made of clear plastic, glass,
or foil. A second substrate that is made of similar material is used to cover the
OLED. The first substrate and the second substrate are hermitically sealed with a
frit, encasing the OLED in a package (i.e., glass package).
[0003] During operations, the anode and the cathode (i.e., two electrodes) facilitate the
flow of current through the glass package. When electricity is applied to the OLED,
charge carriers (holes and electrons) are injected through the electrodes into the
organic layers. As holes and electrons flow and are combined between the organic layers
photons are produced to generate light.
[0004] In a number of applications OLEDs are considered as the replacement technology for
the next generation of Liquid Crystal Display (LCD) and Light Emitting Diode (LED)
based applications. Conventional OLEDs have a number of advantages. For example, OLEDs
are found to be thinner, lighter, and more flexible than the crystalline layers in
an LED or LCD. Since the light-emitting layers of an OLED are lighter, the substrate
of an OLED can be flexible instead of rigid. In addition, OLEDs are brighter than
LEDs, do not require backlighting like LCDs, and consume much less power than LCDs.
These advantages are especially important for battery-operated devices such as cell
phones and mobile computers. Lastly, OLEDs are easier to produce, can be made to large
sizes, and have large fields of view. As a result of these advantages, current applications
for OLEDs include small-screen devices such as cell phones, personal data assistants
(PDAs), digital cameras, as well as large-screen applications such as the big-screen
televisions of the future.
[0005] However, OLEDs do have a number of shortcomings. Conventional OLED manufacturing
is very expensive. One issue is that OLEDs are susceptible to damage from exposure
to the atmosphere. Exposing the organic layers to moisture and oxygen may cause a
reduction in the useful life of an OLED. For example, OLED performance rapidly degrades
in the presence of even a minute amount of moisture. To address this problem, during
manufacturing, an OLED must be hermetically sealed.
[0006] In conventional OLEDs, hermetic sealing is accomplished by dispensing a frit pattern
between two substrates and melting and sealing the frit to create a hermetically sealed
airtight glass package. Conventional methods of melting and sealing the frit pattern
are performed with a laser.
[0007] There are a number of problems with forming a hermetic seal by using convention laser
sealing methods. Electrical leads exit the glass packet to connect the OLED to other
circuits. As a result, the sealing process must accommodate the electrical leads when
creating the hermetic seal. Therefore, the frit must be deployed and the laser must
be applied in such a way that a hermetic seal is maintained in spite of the electrical
leads that cross the frit pattern.
[0008] In addition, using a laser causes a variety of negative thermal effects on the OLED.
For example, the frit pattern must be dispensed on the substrate far enough away from
the organic material so that the laser sealing process does not cause a thermal defect
in the organic material. In addition, non-uniform laser characteristics may cause
thermal damage. For example, if the laser changes in intensity profile, power, or
beam size, etc., the laser may cause a non-uniform bond across the width, and length
of the frit pattern, resulting in a poor hermetic seal.
[0009] One conventional method of laser sealing uses an optical mask to mitigate the problems
associated with sealing across electrical leads and the thermal effects that result
from sealing. However, the mask reduces useful laser power for sealing and as a result,
impacts the quality of the seal and time required for sealing. Ultimately, quality
and time impact the cost to manufacture and the useful life of an OLED-based product.
[0010] Therefore, it would be beneficial to address the problems associated with laser sealing
an OLED. It would be beneficial to laser seal without the mask which impacts speed
and quality. Lastly, it would be beneficial to seal in a manner that improves sealing
strength and seal uniformity, which would ultimately increase the lifetime of OLED-based
products.
[0012] WO 2007/067533 A2 discloses a method of sealing comprising a substrate and a frit pattern, wherein
a laser beam is focused onto the frit pattern.
[0013] US 2006/082298 A1 discloses a method of sealing an OLED using a diffuser to convert a laser beam, focusing
the laser beam onto a frit pattern and changing at least one the characteristic of
the laser beam as the laser beam traverses the frit pattern.
Summary of the Invention
[0014] The present invention provides a method of sealing an OLED according to claim 1.
[0015] In accordance with the teachings of the present application a method is presented
that result in a stronger, more uniform hermetic laser seal of an OLED. A beam shaper
dynamically adjusts various characteristics of the laser beam and laser operations
such as the shape, size and the intensity profile to achieve a stronger and more uniform,
hermetic, laser seal of an OLED. The beam shaper comprises an optical system that
enables dynamic changes to characteristics of the laser beam such as the laser beam
shape and intensity profile in real-time during the sealing process. As such the laser
beam shape and intensity profile is adjusted during sealing to accommodate electrical
leads, changes in the frit pattern, and the thermal issues associated with laser sealing
an OLED.
[0016] The beam shaper is implemented with several lenses that can be used in combination
to change beam shape and several characteristics of the beam. As a result, the beam
shaper provides variable beam shapes without requiring an optical mask to achieve
high speed, uniform hermetic sealing of OLED devices. In one embodiment, the beam
size in both the x and y directions can be independently adjusted to match a frit
pattern including corner curvature, directional changes, and height variation of the
frit pattern. In addition, both the laser power and the sealing speed may also be
dynamically adjusted and vary along the frit pattern to achieve the best sealing performance.
[0017] The beam shaper may comprise a first lens, a second lens, a distance between the
first lens and the second lens, and a diffuser, the method may comprise the steps
of generating a first laser beam spot with the beam shaper; traversing a frit pattern
with the first laser beam spot; and generating a second laser beam spot with the beam
shaper during traversal of the frit pattern.
[0018] In accordance with the teachings of the present invention, a beam shaper capable
of achieving unique beam intensity profiles such as flat-top, annular, M-shaped, with
different shapes such as rectangular, circular, and elliptical is provided. The beam
shaper is implemented by inserting an optical diffuser between the lenses of an optical
system to redistribute laser beam intensity. As the optical system is implemented
with the diffuser, the beam intensity profile is controlled by the diffuser while
the beam size and shape are controlled by varying the relative distance between the
lenses. As a result, a variety of beams can be achieved for reliable hermetic sealing.
[0019] In one embodiment, the beam shaper generates an annular beam or M-shaped beam with
lower power in the center, higher power at the edges, and a precisely controlled power
intensity ratio (i.e., valley to peak ratio). Compared with a conventional Gaussian
laser beam with a Gaussian intensity profile, the reshaped beam can result in a uniform
temperature distribution across the frit, better utilization of frit width, stronger
bonding strength, less thermal effect on the adjacent components, and less damage
to the substrates.
[0020] As such, a beam shaper implemented in accordance with the teachings of the present
invention can be used to meet all requirements for hermetic sealing of OLED devices.
The beam shaper provides improved flexibility, productivity, better sealing performance
and mechanical strength. The beam shaper produces a variety of beam profiles to match
specific frit sizes and patterns. The variety of beam profiles eliminates the need
for custom masks. As such, a sealing system or station implemented in accordance with
the teachings of the present invention can be used for mass production of a number
of different products. In addition, by eliminating the mask and alignment process,
the pre-production time is saved and total cost is reduced. Lastly, a beam shaper
used in conjunction with low-loss glass materials can be lossless so that most of
the laser power can be focused on the frit and sealing speed can be improved.
[0021] Ultimately, a beam shaper implemented in accordance with the teachings of the present
invention can result in better sealing performance and stronger mechanical strength.
When the beam profile is matched with the frit width, the sealing quality can be improved
considerably. With the majority of the laser light (power) focused on the frit, the
thermal effect on the adjacent areas is mitigated. As such, the beam shaper can provide
more uniform heating (frit temperature), better utilization of frit width, stronger
bonding to the substrate, less thermal effect on the adjacent components, and less
damage to the substrate.
Brief Description of the Drawings
[0022] The accompanying drawings, which are incorporated in and constitute a part of this
specification, illustrate certain aspects of the instant invention and together with
the description, serve to explain, without limitation, the principles of the invention.
Fig. 1 displays a schematic of a beam shaper implemented in accordance with the teachings
of the present invention;
Fig. 2 displays a variable beam traversing along a frit pattern;
Fig. 3. displays one embodiment of the optical system implemented in the beam shaper
shown in Fig. 1 useful for understanding the invention;
Fig. 4 displays a plot of the beam size vs. lens location;
Fig. 5 displays a beam shape (outlined by a number of dots surrounding a central dot)
on a focal plane as implemented in accordance with the teachings of the present invention;
Fig. 6 displays one embodiment of a lens housing for achieving adjustable beam size
and shape;
Fig. 7 displays microstructure of a diffuser surface consisting of numerous areas
with specific patterns and thickness;
Fig. 8A shows a simulation of a beam intensity achieved by adding a beam diffuser
between the lenses of the beam shaper shown in Fig. 1;
Fig. 8B shows the intensity profile vs. location;
Fig. 9 displays a photograph of rectangular beam achieved with a diffuser implemented
in accordance with the teachings of the present invention;
Fig. 10 displays an intensity vs. location plot of a beam generated with a diffuser;
Fig. 11 displays a normalized frit temperature (normalized to frit center temperature)
vs. laser exposure time at different locations when a reshaped beam with intensity
profile shown in Fig. 10 is used.
Detailed Description of the Invention
[0023] In accordance with the teachings of the present invention a method for sealing an
OLED is presented. In one embodiment a method for dynamically shaping a laser beam
onto a frit pattern is presented. The method enables dynamic shaping of a laser beam
and dynamic changes to characteristics of the laser beam in real-time during the laser
sealing process. As such, variations in the frit pattern may be accommodated and a
better hermetic seal may be achieved. A beam shaper is implemented using a plurality
of optical lenses (i.e., optical system) that are selected or are adjusted relative
to each other to dynamically shape a laser beam in real-time during the sealing process.
In another embodiment, a diffuser is positioned within the optical system and the
combination of the optical lenses and the diffuser are selected and/or adjusted to
dynamically shape a laser beam footprint (i.e., beam size and shape) and dynamically
change the characteristics of the laser beam, such as the shape, size, and the intensity
profile in real-time during sealing. Using the optical lenses and the diffuser, a
variety of beam shapes ranging from elliptical, to square, to donut shaped, etc may
be realized. In addition, in one embodiment, as the beam shape is adjusted the intensity
profile may be dynamically changed to address variations in the frit and result in
a better seal.
[0024] Fig. 1 displays a schematic diagram of a beam shaper implemented in accordance with
the teachings of the present invention. A laser beam 1 is applied to seal a frit 8
positioned between a cover substrate 7 and a support substrate 9. In one embodiment,
the laser beam 1 may be generated using a laser system 1A such as a diode laser based
system. The laser beam 1 may be implemented as single mode beam with diffraction-limited
beam quality, or as a multi-mode beam, etc. In one embodiment, the laser beam 1 is
delivered by an optical fiber to an optical system 2. The optical fiber can be single
mode or multimode fiber. It should be appreciated that a variety of laser beam generating
devices may be implemented and are contemplated within the scope of the present invention.
The optical system 2 includes a number of lenses (3, 5, 6) and a diffuser 4 for shaping
the laser beam 1. The frit 8 is positioned between a cover substrate 7 and a support
substrate 9.
[0025] During operations, the optical lenses (3, 5, 6) are adjusted relative to each other
to re-image the laser beam 1 to a desirable beam shape and intensity profile. For
example, a laser beam 1 is re-imaged by the three lenses (3, 5, 6) onto the frit 8
through the cover substrate 7. The laser wavelength is chosen for optimal performance
of both substrates and frit so that the laser is transparent to the substrates but
absorbed by the frit. The laser radiation absorbed by the frit 8 leads to rapid local
heating to melt the frit 8 and to form a hermetic seal between the two glass substrates
(7, 9). During operations there is movement of the laser relative to the substrates
(7, 9) and frit 8. For example, in one embodiment the laser beam 1 may remain stationary
and the substrates (7, 9) and the frit 8 may move. In a second embodiment the optical
system 2 and laser 1 may move and the substrates (7, 9) and frit 8 may remain stationary.
In a third embodiment both the optical system 2 and the substrates (7, 9) may move
relative to each other. As a result, the laser continuously melts the frit and finally
forms a hermetic seal of the two substrates (7, 9).
[0026] Fig. 2 displays a variable laser beam traversing along a frit pattern 200. For example,
Fig 2 displays the frit 8 of Fig. 1 as the frit 8 would look from the top view. A
frit pattern 200 is shown (i.e., frit 8 of Fig. 1 from a top view). The frit pattern
200 changes and includes straight sections shown by 202 and curved sections shown
as 204. Organic material 206 may be deployed within the boundaries of the frit pattern
200. In addition, electrical leads 208 may cross the path of the frit pattern 200.
The organic material 206 is typically spaced from the frit pattern 200 as shown by
210 to avoid thermal effects resulting from the laser sealing. The footprint (212,
214) of a variable laser beam is also shown. The footprint 212 and the footprint 214
represent the same laser beam (i.e., at different times) reshaped by the beam shaper
depicted in Fig. 1 as the laser beam traverses different sections of the frit pattern
200.
[0027] The footprint 212 may represent the variable laser beam as the laser traverses a
straight portion 202 of the frit pattern 200. As such, footprint 212 may be implemented
as an elliptical beam which may be more appropriate since an elliptical beam may cover
more surface area at a higher speed on straight sections 202, while remaining within
the boundaries of the straight sections 202. The footprint 214 may represent the variable
laser beam as the laser traverses the curved portion 214 of the frit pattern 200.
As such, footprint 214 may be implemented as a circular beam which may be more appropriate
since a circular footprint may provide the appropriate dimensions and maintain uniform
beam characteristics as the laser beam traverses the curved sections 204 of the frit
pattern 200.
[0028] In accordance with the teachings of the present invention, during operations, a laser
beam may be implemented with a first footprint such as an elliptical footprint 212,
move at a first speed, operate at first power, and include a first intensity profile
and, for example, along the curved portion 204 of the frit pattern 200 the laser beam
may be implemented with a second footprint such as a circular footprint 214, move
at a second speed that is different from the first speed, operate at a power level
that is different from the first power level, and provide a second intensity profile
that is different from the first intensity profile. As such, the laser beam may be
dynamically adjusted, in real-time, during sealing, to accommodate any non-uniformity
in the frit pattern. In one embodiment, non-uniformity may include any changes in
frit pattern, such as height, width, direction, etc., as well as any additional issues
that effect the sealing operations or preclude a strong hermetic seal such as spacing
from the organic material, obstructions in the frit pattern, requirements for temperature
distribution across the frit (i.e., uniform distribution), proper utilization of frit
width, strong bonding strength, thermal effect on the adjacent components, damage
to the substrates, etc.
[0029] The OLED is sandwiched between a glass substrate and a cover glass which are sealed
together with a frit to form a glass package. The frit seal formed by the frit pattern
200 is normally positioned on the outer edge of the glass package. The electrical
leads 208 pass through the frit pattern 200 and connect to external circuits. The
presence of the electrical leads 208 makes the hermetic sealing difficult as the non-transparent
electrical leads 208 may cause a variation or discontinuity in the frit pattern 200
and have different absorption properties which may create uneven laser absorption
and effect sealing quality. The electrical leads 208 also induce different dynamic
thermal behavior because of the difference of thermal conductivity. In an example
useful for understanding the invention, the laser power varies when the laser encounters
the electrical leads 208 so that the frit temperature can be constant to obtain best
sealing quality. In one embodiment, the beam should be slightly smaller than the frit
to avoid unwanted thermal effects on the electrical leads and the organic material
206.
[0030] In another embodiment, it may be beneficial to have a laser beam cover a long section
of the frit so that it can seal the frit at a higher speed, as there is a relationship
between the shape, the power, and the speed of sealing (i.e., traversing the laser
beam across the frit pattern). For example, a first beam with a first shape and higher
power may traverse the beam faster than a second beam, with a second shape, and lower
power. In another example, changing the shape to elliptical, and adjusting the power,
and the speed of sealing reduces residual stress during sealing as the frit can be
heated and cooled slower with an elliptical beam than with a small circular beam given
that the frit has longer reaction time with the laser beam (i.e., given that the elliptical
shape takes a longer time to traverse a spot on the frit) and thus reduces temperature
gradient and induced stress.
[0031] Fig. 3 shows an optical system implemented useful for understanding the teachings
of the present invention. Fig. 3 represents the three lenses (3, 5, 6) of the beam
shaper 2 shown in Fig. 1. Lens 302 corresponds to lens 3 of Fig. 1, lens 304 corresponds
to lens 5 of Fig. 1 and lens 306 corresponds to lens 6 of Fig. 1. In one embodiment
a light source such as a laser diode 300 generates a laser which traverses through
a first lens 302, a second lens 304, to a third lens 306. The laser source 300 can
be a diode laser or other type of laser, such as Nd:YAG laser, fiber laser, or diode-pumped
solid-state laser. The laser beam may be transported by an optical fiber.
[0032] In one embodiment, the first lens 302 may be implemented with a cylindrical lens.
The second lens 304 may be implemented with a cylindrical lens and the third lens
306 may be implemented with an aspherical lens. In one embodiment, the two different
cylindrical lenses (302, 304) may be used to achieve different image magnifications
in two perpendicular directions (i.e., X and Y), since a cylindrical lens only effects
beam propagation in one direction. The aspherical lens provides a simple way of reducing
optical aberrations. As a result, a circular beam can be converted into an elliptical
beam and vice versa. Therefore, in one embodiment the two cylindrical lenses may be
used to adjust the size of the laser beam and the aspherical lens may be implemented
to adjust the direction of the laser beam.
[0033] In one embodiment, the distances of lenses from the laser diode are 15.77mm, 40mm,
and 35.6mm, respectively and lens parameters as shown in Table I provided below. In
one embodiment, the optical system of Fig. 3 includes of a number of optical lenses
(302, 304, 306) that can provide a variable elliptical beam with aspect ratios ranging
from 1.5 to at least 3.0. The aspect ratio of the laser beam may be adjusted by varying
the distance between the two cylindrical lenses. The aspect ratio of the beam is appropriately
chosen so that the sealing along the frit is optimal while thermal effect on the adjacent
components is minimal. For example, a laser diode fiber 300 with a diameter of 1.5
mm can be converted into a 0.8X1.5 mm elliptical beam. The elliptical beam can be
changed from 0.8X1.5 mm to 0.82X2.2 mm by changing the distance shown as 308 between
the lens 302 and 304.
Table I. Lens parameters
Lens |
|
Type |
Focal length |
|
302 |
|
Cylindrical Plano Convex |
25mm |
|
304 |
|
Cylindrical Plano Convex |
150mm |
|
306 |
|
Aspherical Lenses |
34.5mm |
|
[0034] Fig. 4 displays a plot of the beam size vs. lens location. Fig. 4 depicts how a change
in the distance between lens 304 and lens 302 of Fig. 3 (i.e., 308 of Fig. 3) affects
the shape of the laser beam. As shown in the graph of Fig.4 a change in distance between
lens 304 and lens 302 substantially changes the beam shape in the Y-axis but has very
little impact in the X-axis. This unique feature allows the elliptical footprint of
the laser beam to change at a corner of a frit pattern as shown in Fig. 2 (i.e., 214)
so that it can match the changes and orientation of the frit width enabling the laser
beam to traverse the corner with the appropriate laser characteristics and a better
hermetic seal.
[0035] In accordance with the teachings of the present invention, it must be noted that
changing beam shape leads to a power intensity change which may require a sealing
speed change in order to obtain an optimal seal. The power difference can be estimated
using beam size difference when the same laser power is used. For example, the power
intensity difference between the straight line using a 0.82X2.2 mm beam and at the
corner using a 0.8X1.5 mm beam can be [0.82X2.2/(0.8X1.5)=1.5] 50% assuming the same
laser power. To obtain the same seal condition, the frit should move approximately
50% faster at the corner or alternatively the laser power should be approximately
50% lower if a constant speed is desired.
[0036] Fig. 5 displays an example of the beam shape after the beam is reshaped by the beam
shaper (i.e., Fig. 1). The eight dots surrounding a central dot outline the edge of
the elliptical beam. A circular laser source (i.e., 300 of Fig. 3) is generated and
the elliptical beam results after being processed through the optical system shown
as Fig. 3. In accordance with the teachings of the present invention, when two cylindrical
lenses (302, 304) are adjusted relative to each other the elliptical beam shown in
Fig. 5 may be generated from a curricular laser source (i.e., 300).
[0037] Fig. 6 displays one embodiment of a lens housing for achieving adjustable beam size
and shape. The lens housing represents the physical apparatus used to implement the
beam shaper of Fig. 1. In one embodiment of the present invention the adjustment of
the lenses is achieved by mounting the lenses in the mechanical housing of Fig. 6.
As shown in Fig.6 the first lens 610 is mounted with respect to a first fiber mount
600 and pre-aligned, while the second cylindrical lens 620 and the aspherical lens
630 are mounted in a different housing. In one embodiment, distance changes between
lenses is achieved by moving the lens 620 and 630 together while keeping the fiber
and the lens 610 location unchanged. The distance change can be made manually or by
a computer controlled stage. During the distance change, all lenses should remain
on the same optical axis to mitigate optical distortion. One approach to changing
the distance between lenses uses cylindrical mounts in which all optical components
are mounted in housings using high precision cylindrical tubes. Each high precision
tube has the same outer diameter and is inserted into another tube having the same
inner diameter. The gaps between the outer tube and inner tubes should be less than
20 microns. The orientation of lens housing is kept in alignment by using additional
pins sitting in the slot of outer tubes. The lenses can then be mounted in the housing
using conventional lens mounting methods or glued using adhesive. In one embodiment,
each lens housing must have a high precision reference surfaces for registration of
the lens position. The position tolerance for each lens is normally less than 10 microns.
[0038] It should be appreciated that while one lens configuration is shown and discussed
each lens can be replaced by a more sophisticated multiple element lens consisting
of a number of convex and concave lenses to optimize performance. For example, in
one embodiment, the aspherical lens can also be replaced with a number of spherical
lenses to achieve similar functionality.
[0039] In accordance with the teachings of the present invention, a variety of methods may
be implemented to change the beam size. In one embodiment, the beam size (i.e., footprint)
on the frit can be adjusted by defocusing the beam when a large beam is required.
In this case, the beam can be increased to several millimeters. A larger beam size
can also be achieved by changing the lens focal lengths so that a greater magnification
is achieved. In one embodiment, each cylindrical lens can be replaced with a combination
of convex and concave cylindrical lenses so that the effective focal length can be
adjusted by varying the distance between the lenses.
[0040] Fig. 7 displays a diffuser implemented in accordance with the teachings of the present
invention. In one embodiment, a diffuser is defined as a diffractive optic element
that receive a laser beam and redistribute the light into virtually any pattern desired.
[0041] In accordance with the teachings of the present invention, a diffuser with a microstructure
having different shapes and thickness on the surface redirects the input beam by changing
the phase of each segment of the beam. In addition, the diffusers are not sensitive
to alignment and do not effect the polarization of the input beam. They can be made
out of fused silica, silicon, plastic, or other materials covering wavelengths from
193nm to 20um. With the help of micro-processing, diffusers implemented in accordance
with the teachings of the present invention can be made with minimal zero order hot
spots (often less than 1%) and efficiencies as high as 95%. The structures that make
a diffuser work are called scatter centers. These are the elementary surface units
that direct incoming light rays into different directions. The clustering of millions
of scatter centers over a large area combines to provide the scattering properties
of the diffuser. The typical scatter center is a microlens element, as illustrated
in Fig. 7. To achieve greater than 90% conversion efficiency, each scatter center
is individually designed to implement a certain light-control task. The surface structure
as well the statistical distribution of scatter centers is carefully designed and
fabricated.
[0042] The use of optical diffuser makes it possible to achieve almost any shape of laser
beam with any shape of beam intensity profile. In one embodiment of the present invention
a diffuser may be used to adjust a characteristic of the laser beam, such as beam
intensity profile, divergence angle, and beam shape. For example, the diffuser may
be used to adjust the intensity profile of the beam. In some cases, a beam with a
unique intensity profile is required such as flat-top and donut-like to optimize seal
strength and quality. This can be achieved by inserting a beam diffuser between the
lenses. In one embodiment, to achieve strong sealing with uniform heating, a beam
having a central deepened intensity profile (i.e. M-shaped profile) is required. The
key to achieving such an intensity profile is to choose the diffuser capable of converting
a Gaussian intensity profile into an M-shaped profile with minimal residual zero-order
(i.e. central peak).
[0043] In frit sealing, the beam shape and intensity profile are especially important for
achieving strong sealing. In one embodiment, the diffuser is used to convert a Gaussian
beam with higher intensity in the center into a donut-shaped beam with lower intensity
in the center than the edges of the beam. Fig. 8A displays a beam intensity profile,
which is achieved by adding a beam diffuser between the lenses of the beam shaper
shown in Fig. 1. Fig. 8B is an example of the intensity profile vs. location. The
diffuser redistributes power from an original circular beam to the edge and the lenses
re-image the beam into an elliptical ring shown as Fig. 8A. In this embodiment, the
beam intensity profile is controlled by the diffuser while the beam size is controlled
by the lenses. Using a different diffuser can change the power intensity without changing
the beam shape while changing the lens distance leads to different beam sizes without
changing beam intensity profile. Therefore, the beam shaper implemented in accordance
with the teachings of the present invention (i.e., Fig. 1) can control the beam size
and power intensity independently.
[0044] In one embodiment, the diffuser is used to convert a circular Gaussian beam into
a rectangular-like beam with fairly uniform intensity over the beam or slightly higher
intensity around the edges as shown in Fig. 9. In this case, the aspect ratio is controlled
by lens distance as well. When the beam is used for frit sealing, the beam changes
from aspect ratio of approximately 2∼4 along the straight portion while it reduces
to ~1 at corners to avoid potential damage to electrical leads and display elements.
[0045] In accordance with the teachings of the present invention, a new beam profile can
be constructed. The power intensity is lower in the center of the laser beam and increases
as you move from the center of the laser beam to the edge of the laser beam. For a
0.7-mm-wide frit, the ratio of power intensity between frit edge and frit center is
3.23, as shown in Fig. 10. When such a beam is used to illuminate the frit, the temperature
difference across the frit width is noticeably less than that of conventional approach
using a Gaussian beam with an optical mask. This more uniform temperature across the
frit width leads to uniform heating of the frit, therefore the bonding of the frit
to the substrate is more uniform across the width, and better utilization of frit
width is achieved. Since there is more frit bonding area and stronger mechanical strength
this new beam profile can increase the mechanical strength of a sealed OLED device.
In an example useful for understanding the invention, the laser power is reduced when
the beam passes through the area including electrical leads across the frit while
the sealing speed remains unchanged. As the frit volume in the region is smaller than
that of region without electrical leads, reducing power can avoid overheating of the
region and thus prevent the electrical leads from potential damage. The power reduction
is dependent on the size and material of both frit and electrical leads. Normally,
the power should be reduced to less than 15%, preferably, less than 10%.
[0046] It should also be understood that while the present invention has been described
in detail with respect to certain illustrative and specific aspects thereof, it should
not be considered limited to such, as the invention is defined as in the claims.
1. A method of sealing an OLED, the OLED comprising a substrate (7) and a frit pattern
(200) deployed relative to the substrate (7), the method comprising the steps of:
using a diffuser (4) to convert a Gaussian laser beam with higher intensity in the
center of the beam into a laser beam with lower intensity in the center of the laser
beam than at the edges of the laser beam, focusing the laser beam with characteristics
of shape, size and intensity profile, onto the frit pattern (200), wherein a beam
shaper (2) is implemented using a plurality of optical lenses (3, 5, 6) that are selected
or are adjusted relative to each other to dynamically shape the laser beam in real-time
during the sealing process, and wherein the diffuser (4) is positioned within the
plurality of optical lenses (3, 5, 6) and the combination of the optical lenses (3,
5, 6) and the diffuser (4) is selected and/or is adjusted to dynamically shape the
size and shape of the laser beam; and
changing at least one of the said above characteristics of the laser beam as the laser
beam traverses the frit pattern (200).
2. The method of sealing an OLED as set forth in claim1, wherein said at least one of
the characteristics is the shape.
3. The method of sealing an OLED as set forth in claim1, wherein said at least one of
the characteristics is the size.
4. The method of sealing an OLED as set forth in claim1, wherein said at least one of
the characteristics is the intensity profile.
5. The method of sealing an OLED as set forth in claim1, wherein the frit pattern comprises
a straight section (202) and a curved section (214) and the step of focusing the laser
beam is performed on the straight section (202) and the step of changing at least
one of the characteristics of the laser beam is performed on the curved section (214).
6. The method of sealing an OLED as set forth in any one of the preceding claims 1-5,
wherein the optical lenses (3, 5, 6) and the diffuser (4) are used to realize a variety
of beam shapes ranging from elliptical, to square, to donut shaped.
7. The method of sealing an OLED as set forth in any one of the preceding claims 1 to
6, wherein as the beam shape is adjusted the intensity profile is dynamically changed
to address variations in the frit pattern (200).
8. The method of sealing an OLED as set forth in any one of the preceding claims 1 to
7, wherein the beam shaper (2) controls the beam size and the power intensity independently.
9. The method of sealing an OLED as set forth in any one of the preceding claims 1 to
8, wherein the diffuser (4) is used to convert the circular Gaussian beam into a rectangular
- like beam with uniform intensity over the beam or slightly higher intensity around
the edges of the beam.
10. A method of sealing an OLED as set forth in claim 9, wherein an aspect ratio of the
beam is changed from about 2-4 along a straight portion of the frit pattern (200)
to an aspect ratio of about 1 at the corners of the frit pattern (200).
1. Verfahren zum Abdichten einer OLED, wobei die OLED ein Substrat (7) und ein Frittenmuster
(200), das relativ zu dem Substrat (7) eingesetzt ist, umfasst, wobei das Verfahren
die folgenden Schritte umfasst:
Verwenden eines Diffusors (4), um einen Gaußschen Laserstrahl mit höherer Intensität
im Zentrum des Strahls in einen Laserstrahl mit geringerer Intensität im Zentrum des
Laserstrahls als an den Kanten des Laserstrahls umzuwandeln, wobei der Laserstrahl
mit den Eigenschaften Form, Größe und Intensitätsprofil auf das Frittenmuster (200)
fokussiert wird, wobei ein Strahlformer (2) unter Verwendung mehrerer optischer Linsen
(3, 5, 6), die relativ zueinander ausgewählt oder angepasst sind, um den Laserstrahl
dynamisch in Echtzeit während des Abdichtprozesses zu formen, implementiert ist, wobei
der Diffusor (4) innerhalb der mehreren optischen Linsen (3, 5, 6) positioniert ist
und die Kombination der optischen Linsen (3, 5, 6) und des Diffusors (4) ausgewählt
ist und/oder angepasst wird, um die Größe und die Form des Laserstrahls dynamisch
zu formen; und
Ändern mindestens einer der oben beschriebenen Eigenschaften des Laserstrahls, während
der Laserstrahl das Frittenmuster (200) durchläuft.
2. Verfahren zum Abdichten einer OLED nach Anspruch 1, wobei die mindestens eine Eigenschaft
die Form ist.
3. Verfahren zum Abdichten einer OLED nach Anspruch 1, wobei die mindestens eine Eigenschaft
die Größe ist.
4. Verfahren zum Abdichten einer OLED nach Anspruch 1, wobei die mindestens eine Eigenschaft
das Intensitätsprofil ist.
5. Verfahren zum Abdichten einer OLED nach Anspruch 1, wobei das Frittenmuster einen
geraden Abschnitt (202) und einen gekrümmten Abschnitt (214) umfasst und der Schritt
des Fokussierens des Laserstrahls auf dem geraden Abschnitt (202) durchgeführt wird
und der Schritt des Änderns mindestens einer der Eigenschaften des Laserstrahls auf
dem gekrümmten Abschnitt (214) durchgeführt wird.
6. Verfahren zum Abdichten einer OLED nach einem der vorhergehende Ansprüche 1-5, wobei
die optischen Linsen (3, 5, 6) und der Diffusor (4) verwendet werden, um eine Vielzahl
von Strahlformen im Bereich von elliptisch über quadratisch zu ringförmig zu realisieren.
7. Verfahren zum Abdichten einer OLED nach einem der vorhergehende Ansprüche 1 bis 6,
wobei das Intensitätsprofil dynamisch verändert wird, während die Strahlform angepasst
wird, um Schwankungen in dem Frittenmuster (200) zu adressieren.
8. Verfahren zum Abdichten einer OLED nach einem der vorhergehenden Ansprüche 1 bis 7,
wobei der Strahlformer (2) die Strahlgröße und die Leistungsintensität unabhängig
steuert.
9. Verfahren zum Abdichten einer OLED nach einem der vorhergehende Ansprüche 1 bis 8,
wobei der Diffusor (4) verwendet wird, um den kreisförmigen Gaußschen Strahl in einen
rechteckähnlichen Strahl mit gleichmäßiger Intensität über den Strahl oder mit etwas
höherer Intensität in der Nähe der Kanten des Strahls umzuwandeln.
10. Verfahren zum Abdichten einer OLED nach Anspruch 9, wobei ein Seitenverhältnis des
Strahls von etwa 2-4 entlang eines geraden Abschnitts des Frittenmusters (200) zu
einem Seitenverhältnis von etwa 1 an den Kanten des Frittenmusters (200) geändert
wird.
1. Procédé de soudage d'une OLED, l'OLED comprenant un substrat (7) et un motif de fritte
(200) déployé par rapport au substrat (7), le procédé comprenant les étapes suivantes
:
utiliser un diffuseur (4) pour convertir un faisceau laser gaussien ayant une intensité
plus élevée au centre du faisceau en un faisceau laser ayant une intensité plus faible
au centre du faisceau laser qu'aux bords du faisceau laser, focalisant le faisceau
laser avec des caractéristiques de forme, de taille et de profil d'intensité sur le
motif de fritte (200), où un dispositif de mise en forme de faisceau (2) est mis en
oeuvre au moyen d'une pluralité de lentilles optiques (3, 5, 6) qui sont sélectionnées
ou ajustées les unes par rapport aux autres pour mettre en forme dynamiquement le
faisceau laser en temps réel pendant le processus de soudage, et où le diffuseur (4)
est positionné dans la pluralité de lentilles optiques (3, 5, 6) et la combinaison
des lentilles optiques (3, 5, 6) et du diffuseur (4) est sélectionnée et/ou ajustée
pour mettre en forme dynamiquement la taille et la forme du faisceau laser ; et
modifier au moins l'une desdites caractéristiques susmentionnées du faisceau laser
à mesure que le faisceau laser traverse le motif de fritte (200).
2. Procédé de soudage d'une OLED tel qu'énoncé dans la revendication 1, dans lequel ladite
au moins une des caractéristiques est la forme.
3. Procédé de soudage d'une OLED tel qu'énoncé dans la revendication 1, dans lequel ladite
au moins une des caractéristiques est la taille.
4. Procédé de soudage d'une OLED tel qu'énoncé dans la revendication 1, dans lequel ladite
au moins une des caractéristiques est le profil d'intensité.
5. Procédé de soudage d'une OLED tel qu'énoncé dans la revendication 1, dans lequel le
motif de fritte comprend une section droite (202) et une section courbe (214), et
l'étape de focalisation du faisceau laser est exécutée sur la section droite (202),
et l'étape de changement d'au moins une des caractéristiques du faisceau laser est
exécutée sur la section courbe (214) .
6. Procédé de soudage d'une OLED tel qu'énoncé dans l'une quelconque des revendications
précédentes 1 à 5, dans lequel les lentilles optiques (3, 5, 6) et le diffuseur (4)
sont utilisés pour réaliser une variété de formes de faisceaux allant de faisceaux
elliptiques, de faisceaux carrés à des faisceaux en forme de tore.
7. Procédé de soudage d'une OLED tel qu'énoncé dans l'une des revendications précédentes
1 à 6, dans lequel, à mesure que la forme du faisceau est ajustée, le profil d'intensité
est modifié dynamiquement pour tenir compte des variations du motif de fritte (200).
8. Procédé de soudage d'une OLED tel qu'énoncé dans l'une quelconque des revendications
précédentes 1 à 7, dans lequel le dispositif de mise en forme de faisceau (2) contrôle
indépendamment la taille du faisceau et l'intensité de la puissance.
9. Procédé de soudage d'une OLED tel qu'énoncé dans l'une quelconque des revendications
précédentes 1 à 8, dans lequel le diffuseur (4) est utilisé pour convertir le faisceau
gaussien circulaire en un faisceau d'aspect rectangulaire ayant une intensité uniforme
sur le faisceau ou une intensité légèrement plus élevée près des bords du faisceau.
10. Procédé de soudage d'une OLED tel qu'énoncé dans la revendication 9, dans lequel un
rapport de format du faisceau est modifié d'environ 2 à 4 le long d'une partie droite
du motif de fritte (200) à un rapport de format d'environ 1 au niveau des coins du
motif de fritte (200).